AS102 Study Guide - Final Guide: Dark Matter, Baryon
Document Summary
That is the abundance of hydrogen and helium observed today in the oldest stars. In fact, the amount of helium in the whole universe is around 25% with hydrogen making up the rest except for a little bit of lithium. Some of the helium has come from fusion in stars but that process has generated only a small portion of the. Thus, the helium had to have been produced in the early universe. During the 5-minute era of nucleosynthesis conditions were right to form both protons (and neutrons), which combined with electrons to form hydrogen nuclei that fused together to form helium. Chalk another one up for the bb theory! This matter, called dark matter because we can"t see it and yet we know it is there, could make up over 80% of the matter in the universe. Today we"ve pretty much established the existence of dark matter and we wonder what it is.
